RESEARCH ARTICLE
Fine-Scale Cartography of Human Impacts along French Mediterranean Coasts: A Relevant Map for the Management of Marine Ecosystems Florian Holon1,2*, Nicolas Mouquet2, Pierre Boissery3, Marc Bouchoucha4, Gwenaelle Delaruelle1, Anne-Sophie Tribot1, Julie Deter1,2
a11111
1 Andromède Océanologie, 7 place Cassan, 34280 Carnon, France, 2 Institut des Sciences de l’Evolution (ISEM)—UMR 5554 CNRS—IRD—UM, Campus de l’Université de Montpellier, 34095 Montpellier cedex 5, France, 3 Agence de l’Eau Rhône-Méditerranée-Corse, Délégation de Marseille, Immeuble le Noailles, 62 La Canebière, 13001 Marseille, France, 4 Laboratoire Ifremer Environnement Ressources Provence-AzurCorse, Centre Méditerranée—Zone Portuaire de Brégaillon—CS20 330–83507 La Seyne-sur-Mer Cedex, France * [email protected]
OPEN ACCESS Citation: Holon F, Mouquet N, Boissery P, Bouchoucha M, Delaruelle G, Tribot A-S, et al. (2015) Fine-Scale Cartography of Human Impacts along French Mediterranean Coasts: A Relevant Map for the Management of Marine Ecosystems. PLoS ONE 10(8): e0135473. doi:10.1371/journal.pone.0135473 Editor: Carlo Nike Bianchi, Università di Genova, ITALY Received: April 20, 2015 Accepted: July 22, 2015 Published: August 12, 2015 Copyright: © 2015 Holon et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All the data underlying the findings in our study are freely available within the paper, its Supporting Information file and on www. medtrix.fr (IMPACT project). Funding: This work was essentially funded by the Agence de l’Eau RMC (http://www.eaurmc.fr/) and Andromède Océanologie (a commercial funder, http:// www.andromede-ocean.com/). Florian Holon was supported by a PhD grant from LabEX CeMeb (http:// www.labexcemeb.org/) and Andromède Océanologie. Nicolas Mouquet was funded by CNRS (http://www. cnrs.fr/), Pierre Boissery by Agence de l’Eau RMC,
Abstract Ecosystem services provided by oceans and seas support most human needs but are threatened by human activities. Despite existing maps illustrating human impacts on marine ecosystems, information remains either large-scale but rough and insufficient for stakeholders (1 km² grid, lack of data along the coast) or fine-scale but fragmentary and heterogeneous in methodology. The objectives of this study are to map and quantify the main pressures exerted on near-coast marine ecosystems, at a large spatial scale though in fine and relevant resolution for managers (one pixel = 20 x 20 m). It focuses on the French Mediterranean coast (1,700 km of coastline including Corsica) at a depth of 0 to 80 m. After completing and homogenizing data presently available under GIS on the bathymetry and anthropogenic pressures but also on the seabed nature and ecosystem vulnerability, we provide a fine modeling of the extent and impacts of 10 anthropogenic pressures on marine habitats. The considered pressures are man-made coastline, boat anchoring, aquaculture, urban effluents, industrial effluents, urbanization, agriculture, coastline erosion, coastal population and fishing. A 1:10 000 continuous habitat map is provided considering 11 habitat classes. The marine bottom is mostly covered by three habitats: infralittoral soft bottom, Posidonia oceanica meadows and circalittoral soft bottom. Around two thirds of the bottoms are found within medium and medium high cumulative impact categories. Seagrass meadows are the most impacted habitats. The most important pressures (in area and intensity) are urbanization, coastal population, coastal erosion and man-made coastline. We also identified areas in need of a special management interest. This work should contribute to prioritize environmental needs, as well as enhance the development of indicators for the assessment of the ecological status of coastal systems. It
PLOS ONE | DOI:10.1371/journal.pone.0135473 August 12, 2015
1 / 20
Fine-Scale Cartography of Coastal Human Impacts
Marc Bouchoucha by Ifremer (http://www.ifremer.fr/), Gwenaelle Delaruelle and Anne-Sophie Tribot by Andromède Océanologie and Julie Deter by the University of Montpellier (http://www.umontpellier.fr/) and Andromède Océanologie. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Andromède Océanologie, a commercial funder, provided support in the form of salaries for authors (FH, GD, A-ST and JD), but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the "author contributions" section. Competing Interests: The commercial affiliation to Andromède Océanologie of several authors (FH, GD, A-ST and JD) does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.
could also help better apply and coordinate management measures at a relevant scale for biodiversity conservation.
Introduction Oceans and seas are very important for human well-being; their ecosystems provide among the most important ecosystem services: provision of food, natural shoreline protection against storms and floods, water quality maintenance, support of tourism and other cultural benefits, and maintenance of basic global life support systems [1]. The challenge lies in keeping these resources in a sustainable state of use, which is the main objective of the European Union's Marine Strategy Framework Directive (MSFD, 2008/56/EC) by achieving Good Environmental Status (GES) of EU's marine waters. Yet marine ecosystems and marine resources are under severe anthropogenic threats: population growth, land use change and habitat loss, overfishing and destructive fishing methods, illegal fishing, invasive species, climate change, pollution, increased demand for food and a shift in food preference [2]. The human impact is so great that no region can be considered virgin territory [3–5]. Protecting marine biodiversity and the essential ecosystem services it supports is considered a top priority by different authorities: the scientific community, resource managers, national and international policy agreements, including the MSFD and the Convention on Biological Diversity [6] In this context, it is essential to analyze species and habitat distribution, environmental variables and human threats but also their correlations. Spatial distribution of anthropogenic pressures is particularly important because it is the basis of numerous other studies: ecological indicators development, species distribution analysis, design of marine reserves and of conservation plans. In this context, large-scale (continental, worldwide) studies are now commonly conducted while local studies (regional) are lacking [7–9]. Naturally, generalization often leads to an extrapolation of the spatial and temporal scales at which reliable predictions can be made because by definition large-scale models are not able to fully account for fine-grained complexity [10,11]. Moreover, large-scale predictions and their limitations may be particularly hard to understand and to use for regional managers and local policy makers focusing on specific interests (i.e. < 1km² grid cells). There is thus a paradox between the international scale of political will and the local scale of biodiversity conservation, but also a gap between global analyses and what can really be done in the field [12]. Consequently, there is a need to provide managers and stakeholders with local fine-scale information. In order to fill this gap, fine-scale mapping efforts are multiplying in Europe especially in France [13–15], Spain [16–18], Italy [12,19–21] or Greece [22,23] or along the Baltic sea [24]. Because of the high costs to acquire such data, these fine-scale maps are generally funded in order to respond to specific and local objectives (the study of protected areas, a specific habitat [25] or particular features [26], environmental impact assessment [27]). Consequently, they mostly remain local (often a bay) and thus fragmentary (in space but also for the considered habitats and/or pressures) and heterogeneous in their methodology [12]. Moreover they are often available with difficulty: grey literature [15] or communications during conferences [28] instead of publications (but see [29]). All of this can be an obstacle to understand the impact of pressures on coastal marine habitats and thus to make decision at a local and regional scale. Fine-scale (15 x 15 m grid cells) spatial models have been recently developed in order to link multiple pressures with various coastal ecosystem status within a marine protected area [30]. The implementation into geographical information systems (GIS) allows a predictive approach
PLOS ONE | DOI:10.1371/journal.pone.0135473 August 12, 2015
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Fine-Scale Cartography of Coastal Human Impacts
of the consequences of different management alternatives [30–32]. This represents an important decision support tool for choosing efficient management solutions in the face of complex interactions and high uncertainty. Information concerning pressure distribution (presence/ absence of relevant human activities, weighted distance of these activities) have been here successfully used in order to map potential impacts [33–36]. These data are so useful for local managers that they should exist all along the coast. A map of the diverse coastal marine habitats, of coastal pressures and impacts on these habitats extended to the entire coast would have an interest for the local managers and stakeholders but also for regional and national authorities. It would permit to feed the overall think on the coastal use but also highlight conservation and management priorities, compare different sites and management ways and assess the water body quality. The objective of this work is to map and quantify, at a large spatial scale though in fine and relevant resolution for managers, the main drivers and pressures triggering changes within coastal marine ecosystems. In order to reach these objectives, localization of the different pressures exerted and their impacts is needed as much as maps of marine ecosystems. Among numerous seas listed on Earth, Mediterranean presents the particularity of being a biodiversity hotspot facing numerous and strong threats [37–40]. While maps of cumulative human impacts on marine ecosystems exist at the scale of the Mediterranean and Black sea and even at worldwide scale [5,40–42], this information could be completed along the coast. For instance, the resolution used by Micheli et al. [41] within the Mediterranean and Black sea is 1 km² pixels and no data is associated with the first pixels close to the coast, where most anthropogenic pressures are concentrated. Interested in data that could be of real use to local managers and stakeholders, we sampled data from a homogeneous environmental policy context and thus focused on a unique country: France with its 1700 km of Mediterranean coastline, including Corsica. Our goals were to (1) provide the first complete marine coastal habitat map of the French Mediterranean coast (including Corsica), and (2) to quantify and map cumulative impacts to provide the data needed (one pixel = 20 x 20 m) to help the development of an effective marine policy. On these bases, we identified the most and least impacted areas (water bodies), the top threats affecting coastal waters, and the areas representing top priorities for ecosystem-based management and conservation efforts. The cumulative impact map obtained will be useful for local decision makers and thus complementary to large-scale previous works [41].
Materials and Methods Marine habitats The study considers the entire French Mediterranean coastline (including Corsica) included within the 46 water bodies of homogeneous water according to the Water Framework Directive (WFD,2000/60/EC) [43]. Interested in costal-based impacts, we particularly focus on the shallow part: between 0 and -80 m. After a bibliographic synthesis, we gathered and homogenized data on habitat maps; these data were collected by Andromède Océanologie, Agence de l'Eau RMC;Conservatoire du Littoral, DREAL PACA; EGIS EAU, ERAMM, GIS POSIDONIE, IFREMER, Institut océanographique Paul Ricard, Nice Côte d'Azur, TPM, Programme CARTHAM—Agence des Aires Marines Protégées, ASCONIT Consultants, COMEX-SA, EVEMAR, IN VIVO, Sintinelle, Stareso, Programme MEDBENTH, Université de Corse (EQEL), Ville de St Cyr-sur-mer, Ville de Cannes, Ville de Marseille, Ville de St Raphaël, Ville de St Tropez (S1–S3 Figs). Gaps were completed with the program DONIA [44] with a fine scale (1:10 000 map) between 0 and -80 m and a lower resolution (1:25 000) beyond (S1–S3 Figs). Campaigns were
PLOS ONE | DOI:10.1371/journal.pone.0135473 August 12, 2015
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Fine-Scale Cartography of Coastal Human Impacts
led between 2010 and 2014 using first aerial or satellite photography (in order to measure the spatial extent of habitats in shallow waters) and a multi-beam echo-sounder GeoSwath Plus (Kongsberg Geoacoustics LTD) survey (to draw the bathymetry). Then, a side-scan sonar survey (used in more turbid and deeper (< -15 m) waters) was led. By ensonifying a swath of seabed and measuring the amplitude of the backscattered return signals, an image of the seabed was built up with information on the morphology and substrate content. We used a Klein System 3900 with a frequency comprised between 445 and 900 kHz. After that, sonar information was post-treated to determine the potential presence and coverage of underwater habitat representation. All of these data allow achieving a preliminary cartography of benthic habitats. Numerous uncertainties still remained after this preliminary cartography work. Direct observations (“ground-truth points”) were thus needed through diving sessions (around 1600 dives between 0 and -80 m all along the coastline between 2010 and 2014). They included classic dives and “towed dives” that allowed the sampling of 20 920 ground-truth points. During “towed dives”, the diver was actively able to maneuver a “towboard” to maintain a relative constant elevation above the seabed. The towboard was equipped with an underwater GPS transducer providing the accurate position and exact depth of the diver in real-time to the surface operator. The diver equipped with an integrated communication system transmitted a large quantity of information on benthic habitats (community of organisms which lived on, in, or near the seabed, state of the habitat, occurrence of impacts on the habitat). Occasional exploring dives aimed, by means of in situ observation, to clarify data. These dives allowed to recognize the nature of the seabed and to characterize benthic populations. Field work was organized in cooperation with the French water agency (public authority) which gave permission to conduct the work. Field work was also declared to the authorities responsible of the concerned marine parks. The field studies did not involve endangered or protected species. A final continuous habitat map (scale = 1:10 000 between 0 and– 80 m and 1:25 000 beyond in the case of deeper water bodies) was realized comprising eleven habitat classes: Cymodocea nodosa seagrass, Zostera marina and noltii. seagrass, Posidonia oceanica seagrass, dead matte association, infralittoral shingle association, infralittoral soft bottoms, photophilous algae association, coralligenous assemblages, circalittoral soft bottoms, artificial habitats, offshore rocks. Ecosystem data were finally converted into presence/absence 20 x 20 m pixel layers (in order to be adapted to the pixel size related to the anthropogenic pressures, see below); the habitat corresponding to each pixel was defined by the major habitat observed within the grid (percent cover > 50%).
Anthropogenic pressures Drivers and pressures are here defined according to the DPSIR framework (drivers-pressuresstates-impacts-responses) [45] with drivers such as the main socio-economic and sociocultural forces increasing or mitigating pressures on the environment (rapid population expansion for example). Pressures are defined as stresses that human activities induce on the environment (e.g. wastewater), states being the condition of the environment (e.g. water quality or species richness). Impacts are defined as the effects of these pressures on the environment (e.g. biodiversity loss) and responses are what society does in order to improve the environmental situation (e.g. better wastewater treatment or regulation). Impacts may differ according to the ecosystems considered because of their variable vulnerability: all ecosystems are not threatened in the same way (functional impact, scale, frequency) and are not equally sensitive (resistance and recovery time) [46]. Here we modeled the spatial extent of anthropogenic pressures on the marine environment. We only focused on pressures that can be controlled by local stakeholders. Thus we did not take climate change issues and industrial fishing into account contrary to
PLOS ONE | DOI:10.1371/journal.pone.0135473 August 12, 2015
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Fine-Scale Cartography of Coastal Human Impacts
Micheli et al. [21] because their control appeals for high-level decisions. In addition to this, climate drivers are not considered among the MSFD’s good environmental status descriptors [47]. Ten different pressures (based on quantitative data) were considered: (1) man-made coastline (big harbours / harbours / artificial beaches, ports of refuge / pontoons, groynes, landfills and seawalls areas), (2) boat anchoring (number and size of boats observed during summer), (3) aquaculture (total area of the farms), (4) urban effluents (capacity, output), (5) industrial effluents (chemical oxygen demand), (6) urbanization (land cover), (7) agriculture (land cover), (8) coastline erosion (land cover), (9) coastal population (size and density considering the inhabitants-residents) and (10) fishing (traditional and recreational fishing areas) [see S1 Text for details]. Even if continuous pressures (e.g. wastewater) are generally distinguished from discrete pressures (e.g a groyne building), low resilience of marine ecosystems (especially Posidonia oceanica beds and coralligenous reefs; [48,49]) allow the combination of both pressures within the same methodology. Data concerning the origin and intensity of these pressures are available in published databases: MEDAM [50], CORINE land cover [51], INSEE [52], MEDOBS data [53] but were also provided by Agence de l’Eau RMC and Ifremer completed with an analysis of satellite-aerial pictures and unpublished data (Andromède Océanologie). Models of the spatial extent of the pressures were built using ArcGIS 10 (ESRI) with a 20-m distance matrix. We applied a pressure curve (type y = ae-bx) considering the distance to the source with a negative exponential shape ranging between 100% (origin) and 0% (no more impact) to each type of pressure. We included the bathymetry to model the spread of each pressure based on literature synthesis and our expert knowledge. Details and parameters of each modeled pressure are given in S1 Text.
Cumulative human impacts We used a cumulative impact model following Halpern et al. [5,25] and Micheli et al. [21]. First, we assembled spatial datasets for n = 10 anthropogenic pressures (value Di) (see S1 Text) and m = 11 habitats (value Ej). Secondly, all pressure layers were then log[X+1]-transformed and rescaled between 0–1 to allow direct comparisons. The sum of the different pressures per pixel was calculated. Then, cumulative impacts scores (IC) for each 20 x 20 m pixel were calculated according to Micheli et al. [21] and Halpern et al. [5]: IC ¼
n X m X
Di Ej mi;j
i¼1 j¼1
Where Di is the value of an anthropogenic pressure at location i, Ej is the presence or absence of habitat j and μi,j is the impact weight of anthropogenic pressure I and habitat j [5]. Like Micheli et al. [21], values of impact weights were deduced from Halpern et al. [25]. Cumulative impact to individual ecosystems (IE) was calculated as follows: IE ¼
n X
Di Ej mi;j
i¼1
and impact of individual pressures across all ecosystem types (ID) was calculated as follows: ID ¼
m X
Di Ej mi;j
i¼1
To simplify visualization, impacts were classified in six categories depending on IC values: very high (Ic>10); high (8
Fine-Scale Cartography of Human Impacts along French Mediterranean Coasts: A Relevant Map for the Management of Marine Ecosystems Florian Holon1,2*, Nicolas Mouquet2, Pierre Boissery3, Marc Bouchoucha4, Gwenaelle Delaruelle1, Anne-Sophie Tribot1, Julie Deter1,2
a11111
1 Andromède Océanologie, 7 place Cassan, 34280 Carnon, France, 2 Institut des Sciences de l’Evolution (ISEM)—UMR 5554 CNRS—IRD—UM, Campus de l’Université de Montpellier, 34095 Montpellier cedex 5, France, 3 Agence de l’Eau Rhône-Méditerranée-Corse, Délégation de Marseille, Immeuble le Noailles, 62 La Canebière, 13001 Marseille, France, 4 Laboratoire Ifremer Environnement Ressources Provence-AzurCorse, Centre Méditerranée—Zone Portuaire de Brégaillon—CS20 330–83507 La Seyne-sur-Mer Cedex, France * [email protected]
OPEN ACCESS Citation: Holon F, Mouquet N, Boissery P, Bouchoucha M, Delaruelle G, Tribot A-S, et al. (2015) Fine-Scale Cartography of Human Impacts along French Mediterranean Coasts: A Relevant Map for the Management of Marine Ecosystems. PLoS ONE 10(8): e0135473. doi:10.1371/journal.pone.0135473 Editor: Carlo Nike Bianchi, Università di Genova, ITALY Received: April 20, 2015 Accepted: July 22, 2015 Published: August 12, 2015 Copyright: © 2015 Holon et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All the data underlying the findings in our study are freely available within the paper, its Supporting Information file and on www. medtrix.fr (IMPACT project). Funding: This work was essentially funded by the Agence de l’Eau RMC (http://www.eaurmc.fr/) and Andromède Océanologie (a commercial funder, http:// www.andromede-ocean.com/). Florian Holon was supported by a PhD grant from LabEX CeMeb (http:// www.labexcemeb.org/) and Andromède Océanologie. Nicolas Mouquet was funded by CNRS (http://www. cnrs.fr/), Pierre Boissery by Agence de l’Eau RMC,
Abstract Ecosystem services provided by oceans and seas support most human needs but are threatened by human activities. Despite existing maps illustrating human impacts on marine ecosystems, information remains either large-scale but rough and insufficient for stakeholders (1 km² grid, lack of data along the coast) or fine-scale but fragmentary and heterogeneous in methodology. The objectives of this study are to map and quantify the main pressures exerted on near-coast marine ecosystems, at a large spatial scale though in fine and relevant resolution for managers (one pixel = 20 x 20 m). It focuses on the French Mediterranean coast (1,700 km of coastline including Corsica) at a depth of 0 to 80 m. After completing and homogenizing data presently available under GIS on the bathymetry and anthropogenic pressures but also on the seabed nature and ecosystem vulnerability, we provide a fine modeling of the extent and impacts of 10 anthropogenic pressures on marine habitats. The considered pressures are man-made coastline, boat anchoring, aquaculture, urban effluents, industrial effluents, urbanization, agriculture, coastline erosion, coastal population and fishing. A 1:10 000 continuous habitat map is provided considering 11 habitat classes. The marine bottom is mostly covered by three habitats: infralittoral soft bottom, Posidonia oceanica meadows and circalittoral soft bottom. Around two thirds of the bottoms are found within medium and medium high cumulative impact categories. Seagrass meadows are the most impacted habitats. The most important pressures (in area and intensity) are urbanization, coastal population, coastal erosion and man-made coastline. We also identified areas in need of a special management interest. This work should contribute to prioritize environmental needs, as well as enhance the development of indicators for the assessment of the ecological status of coastal systems. It
PLOS ONE | DOI:10.1371/journal.pone.0135473 August 12, 2015
1 / 20
Fine-Scale Cartography of Coastal Human Impacts
Marc Bouchoucha by Ifremer (http://www.ifremer.fr/), Gwenaelle Delaruelle and Anne-Sophie Tribot by Andromède Océanologie and Julie Deter by the University of Montpellier (http://www.umontpellier.fr/) and Andromède Océanologie. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Andromède Océanologie, a commercial funder, provided support in the form of salaries for authors (FH, GD, A-ST and JD), but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the "author contributions" section. Competing Interests: The commercial affiliation to Andromède Océanologie of several authors (FH, GD, A-ST and JD) does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.
could also help better apply and coordinate management measures at a relevant scale for biodiversity conservation.
Introduction Oceans and seas are very important for human well-being; their ecosystems provide among the most important ecosystem services: provision of food, natural shoreline protection against storms and floods, water quality maintenance, support of tourism and other cultural benefits, and maintenance of basic global life support systems [1]. The challenge lies in keeping these resources in a sustainable state of use, which is the main objective of the European Union's Marine Strategy Framework Directive (MSFD, 2008/56/EC) by achieving Good Environmental Status (GES) of EU's marine waters. Yet marine ecosystems and marine resources are under severe anthropogenic threats: population growth, land use change and habitat loss, overfishing and destructive fishing methods, illegal fishing, invasive species, climate change, pollution, increased demand for food and a shift in food preference [2]. The human impact is so great that no region can be considered virgin territory [3–5]. Protecting marine biodiversity and the essential ecosystem services it supports is considered a top priority by different authorities: the scientific community, resource managers, national and international policy agreements, including the MSFD and the Convention on Biological Diversity [6] In this context, it is essential to analyze species and habitat distribution, environmental variables and human threats but also their correlations. Spatial distribution of anthropogenic pressures is particularly important because it is the basis of numerous other studies: ecological indicators development, species distribution analysis, design of marine reserves and of conservation plans. In this context, large-scale (continental, worldwide) studies are now commonly conducted while local studies (regional) are lacking [7–9]. Naturally, generalization often leads to an extrapolation of the spatial and temporal scales at which reliable predictions can be made because by definition large-scale models are not able to fully account for fine-grained complexity [10,11]. Moreover, large-scale predictions and their limitations may be particularly hard to understand and to use for regional managers and local policy makers focusing on specific interests (i.e. < 1km² grid cells). There is thus a paradox between the international scale of political will and the local scale of biodiversity conservation, but also a gap between global analyses and what can really be done in the field [12]. Consequently, there is a need to provide managers and stakeholders with local fine-scale information. In order to fill this gap, fine-scale mapping efforts are multiplying in Europe especially in France [13–15], Spain [16–18], Italy [12,19–21] or Greece [22,23] or along the Baltic sea [24]. Because of the high costs to acquire such data, these fine-scale maps are generally funded in order to respond to specific and local objectives (the study of protected areas, a specific habitat [25] or particular features [26], environmental impact assessment [27]). Consequently, they mostly remain local (often a bay) and thus fragmentary (in space but also for the considered habitats and/or pressures) and heterogeneous in their methodology [12]. Moreover they are often available with difficulty: grey literature [15] or communications during conferences [28] instead of publications (but see [29]). All of this can be an obstacle to understand the impact of pressures on coastal marine habitats and thus to make decision at a local and regional scale. Fine-scale (15 x 15 m grid cells) spatial models have been recently developed in order to link multiple pressures with various coastal ecosystem status within a marine protected area [30]. The implementation into geographical information systems (GIS) allows a predictive approach
PLOS ONE | DOI:10.1371/journal.pone.0135473 August 12, 2015
2 / 20
Fine-Scale Cartography of Coastal Human Impacts
of the consequences of different management alternatives [30–32]. This represents an important decision support tool for choosing efficient management solutions in the face of complex interactions and high uncertainty. Information concerning pressure distribution (presence/ absence of relevant human activities, weighted distance of these activities) have been here successfully used in order to map potential impacts [33–36]. These data are so useful for local managers that they should exist all along the coast. A map of the diverse coastal marine habitats, of coastal pressures and impacts on these habitats extended to the entire coast would have an interest for the local managers and stakeholders but also for regional and national authorities. It would permit to feed the overall think on the coastal use but also highlight conservation and management priorities, compare different sites and management ways and assess the water body quality. The objective of this work is to map and quantify, at a large spatial scale though in fine and relevant resolution for managers, the main drivers and pressures triggering changes within coastal marine ecosystems. In order to reach these objectives, localization of the different pressures exerted and their impacts is needed as much as maps of marine ecosystems. Among numerous seas listed on Earth, Mediterranean presents the particularity of being a biodiversity hotspot facing numerous and strong threats [37–40]. While maps of cumulative human impacts on marine ecosystems exist at the scale of the Mediterranean and Black sea and even at worldwide scale [5,40–42], this information could be completed along the coast. For instance, the resolution used by Micheli et al. [41] within the Mediterranean and Black sea is 1 km² pixels and no data is associated with the first pixels close to the coast, where most anthropogenic pressures are concentrated. Interested in data that could be of real use to local managers and stakeholders, we sampled data from a homogeneous environmental policy context and thus focused on a unique country: France with its 1700 km of Mediterranean coastline, including Corsica. Our goals were to (1) provide the first complete marine coastal habitat map of the French Mediterranean coast (including Corsica), and (2) to quantify and map cumulative impacts to provide the data needed (one pixel = 20 x 20 m) to help the development of an effective marine policy. On these bases, we identified the most and least impacted areas (water bodies), the top threats affecting coastal waters, and the areas representing top priorities for ecosystem-based management and conservation efforts. The cumulative impact map obtained will be useful for local decision makers and thus complementary to large-scale previous works [41].
Materials and Methods Marine habitats The study considers the entire French Mediterranean coastline (including Corsica) included within the 46 water bodies of homogeneous water according to the Water Framework Directive (WFD,2000/60/EC) [43]. Interested in costal-based impacts, we particularly focus on the shallow part: between 0 and -80 m. After a bibliographic synthesis, we gathered and homogenized data on habitat maps; these data were collected by Andromède Océanologie, Agence de l'Eau RMC;Conservatoire du Littoral, DREAL PACA; EGIS EAU, ERAMM, GIS POSIDONIE, IFREMER, Institut océanographique Paul Ricard, Nice Côte d'Azur, TPM, Programme CARTHAM—Agence des Aires Marines Protégées, ASCONIT Consultants, COMEX-SA, EVEMAR, IN VIVO, Sintinelle, Stareso, Programme MEDBENTH, Université de Corse (EQEL), Ville de St Cyr-sur-mer, Ville de Cannes, Ville de Marseille, Ville de St Raphaël, Ville de St Tropez (S1–S3 Figs). Gaps were completed with the program DONIA [44] with a fine scale (1:10 000 map) between 0 and -80 m and a lower resolution (1:25 000) beyond (S1–S3 Figs). Campaigns were
PLOS ONE | DOI:10.1371/journal.pone.0135473 August 12, 2015
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Fine-Scale Cartography of Coastal Human Impacts
led between 2010 and 2014 using first aerial or satellite photography (in order to measure the spatial extent of habitats in shallow waters) and a multi-beam echo-sounder GeoSwath Plus (Kongsberg Geoacoustics LTD) survey (to draw the bathymetry). Then, a side-scan sonar survey (used in more turbid and deeper (< -15 m) waters) was led. By ensonifying a swath of seabed and measuring the amplitude of the backscattered return signals, an image of the seabed was built up with information on the morphology and substrate content. We used a Klein System 3900 with a frequency comprised between 445 and 900 kHz. After that, sonar information was post-treated to determine the potential presence and coverage of underwater habitat representation. All of these data allow achieving a preliminary cartography of benthic habitats. Numerous uncertainties still remained after this preliminary cartography work. Direct observations (“ground-truth points”) were thus needed through diving sessions (around 1600 dives between 0 and -80 m all along the coastline between 2010 and 2014). They included classic dives and “towed dives” that allowed the sampling of 20 920 ground-truth points. During “towed dives”, the diver was actively able to maneuver a “towboard” to maintain a relative constant elevation above the seabed. The towboard was equipped with an underwater GPS transducer providing the accurate position and exact depth of the diver in real-time to the surface operator. The diver equipped with an integrated communication system transmitted a large quantity of information on benthic habitats (community of organisms which lived on, in, or near the seabed, state of the habitat, occurrence of impacts on the habitat). Occasional exploring dives aimed, by means of in situ observation, to clarify data. These dives allowed to recognize the nature of the seabed and to characterize benthic populations. Field work was organized in cooperation with the French water agency (public authority) which gave permission to conduct the work. Field work was also declared to the authorities responsible of the concerned marine parks. The field studies did not involve endangered or protected species. A final continuous habitat map (scale = 1:10 000 between 0 and– 80 m and 1:25 000 beyond in the case of deeper water bodies) was realized comprising eleven habitat classes: Cymodocea nodosa seagrass, Zostera marina and noltii. seagrass, Posidonia oceanica seagrass, dead matte association, infralittoral shingle association, infralittoral soft bottoms, photophilous algae association, coralligenous assemblages, circalittoral soft bottoms, artificial habitats, offshore rocks. Ecosystem data were finally converted into presence/absence 20 x 20 m pixel layers (in order to be adapted to the pixel size related to the anthropogenic pressures, see below); the habitat corresponding to each pixel was defined by the major habitat observed within the grid (percent cover > 50%).
Anthropogenic pressures Drivers and pressures are here defined according to the DPSIR framework (drivers-pressuresstates-impacts-responses) [45] with drivers such as the main socio-economic and sociocultural forces increasing or mitigating pressures on the environment (rapid population expansion for example). Pressures are defined as stresses that human activities induce on the environment (e.g. wastewater), states being the condition of the environment (e.g. water quality or species richness). Impacts are defined as the effects of these pressures on the environment (e.g. biodiversity loss) and responses are what society does in order to improve the environmental situation (e.g. better wastewater treatment or regulation). Impacts may differ according to the ecosystems considered because of their variable vulnerability: all ecosystems are not threatened in the same way (functional impact, scale, frequency) and are not equally sensitive (resistance and recovery time) [46]. Here we modeled the spatial extent of anthropogenic pressures on the marine environment. We only focused on pressures that can be controlled by local stakeholders. Thus we did not take climate change issues and industrial fishing into account contrary to
PLOS ONE | DOI:10.1371/journal.pone.0135473 August 12, 2015
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Micheli et al. [21] because their control appeals for high-level decisions. In addition to this, climate drivers are not considered among the MSFD’s good environmental status descriptors [47]. Ten different pressures (based on quantitative data) were considered: (1) man-made coastline (big harbours / harbours / artificial beaches, ports of refuge / pontoons, groynes, landfills and seawalls areas), (2) boat anchoring (number and size of boats observed during summer), (3) aquaculture (total area of the farms), (4) urban effluents (capacity, output), (5) industrial effluents (chemical oxygen demand), (6) urbanization (land cover), (7) agriculture (land cover), (8) coastline erosion (land cover), (9) coastal population (size and density considering the inhabitants-residents) and (10) fishing (traditional and recreational fishing areas) [see S1 Text for details]. Even if continuous pressures (e.g. wastewater) are generally distinguished from discrete pressures (e.g a groyne building), low resilience of marine ecosystems (especially Posidonia oceanica beds and coralligenous reefs; [48,49]) allow the combination of both pressures within the same methodology. Data concerning the origin and intensity of these pressures are available in published databases: MEDAM [50], CORINE land cover [51], INSEE [52], MEDOBS data [53] but were also provided by Agence de l’Eau RMC and Ifremer completed with an analysis of satellite-aerial pictures and unpublished data (Andromède Océanologie). Models of the spatial extent of the pressures were built using ArcGIS 10 (ESRI) with a 20-m distance matrix. We applied a pressure curve (type y = ae-bx) considering the distance to the source with a negative exponential shape ranging between 100% (origin) and 0% (no more impact) to each type of pressure. We included the bathymetry to model the spread of each pressure based on literature synthesis and our expert knowledge. Details and parameters of each modeled pressure are given in S1 Text.
Cumulative human impacts We used a cumulative impact model following Halpern et al. [5,25] and Micheli et al. [21]. First, we assembled spatial datasets for n = 10 anthropogenic pressures (value Di) (see S1 Text) and m = 11 habitats (value Ej). Secondly, all pressure layers were then log[X+1]-transformed and rescaled between 0–1 to allow direct comparisons. The sum of the different pressures per pixel was calculated. Then, cumulative impacts scores (IC) for each 20 x 20 m pixel were calculated according to Micheli et al. [21] and Halpern et al. [5]: IC ¼
n X m X
Di Ej mi;j
i¼1 j¼1
Where Di is the value of an anthropogenic pressure at location i, Ej is the presence or absence of habitat j and μi,j is the impact weight of anthropogenic pressure I and habitat j [5]. Like Micheli et al. [21], values of impact weights were deduced from Halpern et al. [25]. Cumulative impact to individual ecosystems (IE) was calculated as follows: IE ¼
n X
Di Ej mi;j
i¼1
and impact of individual pressures across all ecosystem types (ID) was calculated as follows: ID ¼
m X
Di Ej mi;j
i¼1
To simplify visualization, impacts were classified in six categories depending on IC values: very high (Ic>10); high (8
